1. Field of the Invention
The present invention relates to a method and apparatus for making a transport frame and a method and apparatus for processing a transport frame, and more particularly, to a method and apparatus for making and processing a transport frame used to identify synchronization of a packet.
2. Description of the Related Art
With recent developments in information communications technology and network technology, fast transmission of large-capacity data is attracting much attention. In particular, as digital audio devices having high sound quality, such as CDs, DVDs, etc., become widely available, user demand for digital broadcasting of high sound quality is increasing. Therefore, a transport system that effectively transports large-capacity data is needed.
In general transport systems, elementary streams (ESs) are divided into packets and transported, and the packets are loaded in a frame. The frame including the packets is transported to a receiver, which, in turn, separates the packets from the frame in order to extract the ESs. Thus, a method of identifying packets in order to extract ESs from a received frame is needed.
In particular, as for transport frames having consistent sizes, an integral number of packets may not be loaded in each of the transport frames. In other words, a packet may be transported with a front part of the packet being loaded in a first frame and the other part thereof being loaded in a second frame. This form of transportation does not cause any problems when the first and second frames are both received. However, when only the second frame is received, the packet partially loaded in the second frame cannot be used. Thus, the start location of the next packet needs to be searched for in the second frame. However, it is difficult to find the start location of the next packet because the start location of the second frame is not the same as that of a packet.
FIG. 1A illustrates an embodiment of a conventional method of identifying packets included in a frame.
Referring to FIG. 1A, packets 120 are transmitted by being loaded in N transport frames 110-1 through 110-N. Each of the packets 120 is accompanied by synchronization information 130. The packets 120 accompanied by the synchronization information 130 are consecutively loaded in the transport frames 110-1 through 110-N so as to be transported.
The receiver receives the transport frames 110-1 through 110-N, separating the packets 120 therefrom, and extracts the ESs from the packets 120. The packets 120 are divided from each other by using the synchronization information 130.
As described above, according to the conventional method of identifying the packets 120 by adding the synchronization information 130, the packets 120 are identified by reading the synchronization information 130 during a depacketizing process. However, because the validity of the read-out synchronization information 130 is not guaranteed, a special algorithm or process for verifying whether the synchronization information 130 is valid is needed. Additionally, the addition of the synchronization information 130 reduces data efficiency.
FIG. 1B illustrates another embodiment of a conventional method of identifying packets included in a frame.
Referring to FIG. 1B, an integral number of packets 120 are transmitted by being loaded in the transport frame 110-N. The packets 120 are consecutively loaded in the transport frame 110-N, and the number of packets to be loaded in the transport frame 110-N is always an integer. By designing the transport frame 110-N as described above so that only an integral number of packets 120 are loaded in the transport frame 110-N, the start location 111 of the transport frame 110-N is equal to the start location 121 of a packet, and thus the packets 120 can be identified.
However, the conventional method illustrated in FIG. 1B needs a special packet structure corresponding to the type of transport frame. Thus, an existing packet structure may not be used. Additionally, even when a new packet configuration needs to be designed, it is affected by the size of a frame, so that it is actually impossible to design an independent packet configuration.
FIG. 1C illustrates another embodiment of a conventional method of identifying packets included in a frame.
Referring to FIG. 1C, the packets 120 are transported by being loaded in the transport frame 110-N. The packets 120 are consecutively loaded in the transport frame 110-N. When the size of the transport frame 110-N is not an integral multiple of the size of each packet 120, an extra space 130 is generated. The extra space 130 is filled with padding data.
By filling the extra space 130 of the transport frame 110-N with the padding data as described above, the start location 111 of the transport frame 110-N can be aligned with the start location 121 of a packet. Consequently, the packets 120 can be identified.
However, the addition of the padding data to the extra space 130 of each frame in the conventional method illustrated in FIG. 1C denotes a waste of a channel for transporting data corresponding to the extra space 130 filled with the padding data.
As described above, in order to identify the start locations of packets included in each of transport frames having consistent sizes, additional data such as synchronization information or padding data is needed, or the size of each packet should be controlled so that an integral number of packets are loaded in a transport frame. Therefore, the data transmission efficiency is degraded, or a configuration of packets cannot be designed independently.